1. Field of the Invention
The present invention relates to an image processing apparatus, and a processing method and a non-transitory computer-readable storage medium for the same.
2. Description of the Related Art
There is a conventional technique whereby information about a lesion within a medical image, or probe position information is displayed on a body mark that represents the approximate shape of a target object in order to help manipulate the probe during an ultrasound examination or to produce a medical document such as an electronic chart or an image diagnostic report.
For example, Japanese Patent Laid-Open No. 2008-086742 (hereinafter referred to as Literature 1) discloses a technique for finding a conversion rule that performs coordinate conversion from a position on a patient's breast during an ultrasound examination to a standard body mark that represents a breast, and displaying the position of an ultrasonic probe on the body mark (after normalizing it to a body mark coordinate system). Also, Japanese Patent Laid-Open No. 2008-279272 (hereinafter referred to as Literature 2) discloses a technique for producing a 3D body mark by the volume rendering of a target object imaged by MRI apparatus or X-ray CT apparatus, and superposing a display of a graph representing the position of the probe and the position of a lesion on the 3D body mark. With this technique, probe manipulation can be facilitated when a physician is looking for a lesion during ultrasound examination.
In the area of breast oncology, image diagnosis is sometimes performed by a procedure in which the condition of a lesion is imaged and observed using an ultrasound apparatus after identifying the position of the lesion within an image of a breast captured with an MRI apparatus.
In a typical imaging protocol in a breast oncology department, imaging with an MRI apparatus is usually performed in a prone position (face down), and imaging with an ultrasound apparatus in a supine position (face up). In such situations, the physician first identifies the position of the lesion from an MRI image taken in a prone position. Then, deformation of the breast (physical deformation) attributable to different imaging sites is taken into account, and the position of the lesion in the supine position is estimated from the identified position of the lesion. An image is then taken of this estimated position with an ultrasound apparatus.
However, in some cases there is an extremely large amount of breast deformation (physical deformation) attributable to different imaging sites, and the position of the lesion in a supine position estimated by the physician may be very different from the actual position.
Such situations can be dealt with, for example, by using the method of “T. Carter, C. Tanner, N. B. Newman, D. Barratt and D. Hawkes, MR Navigated Breast Surgery Method and Initial Clinical Experience” (MICCAI 2008, Part II, LNCS 5242, pp. 356-363, 2008) (hereinafter referred to as Literature 3), subjecting an MRI image taken in a prone position to physical conversion, and virtually producing an MRI image taken in a supine position. With this method is used, the position of a lesion on the supine position MRI image produced virtually can be calculated on the basis of physical conversion information from prone position to supine position. Also, the position of the lesion on this image can be found directly by the physician by reading the virtual supine position MRI image.
If the precision is high in this physical conversion, then when the lesion is imaged from a subject in a supine position, the actual lesion will be close to the lesion shown in the virtual supine position MRI image, so imaging should be performed in this region.
Using this physical conversion technique and the method disclosed in the above-mentioned Literature 2 as a basis, a supine position 3D body mark can be produced by performing physical conversion of an image of a target object captured in a prone position into an image of a target object captured in a supine position. Furthermore, probe manipulation can be facilitated when a physician is searching for a lesion during an ultrasound examination by superposing a display of a graph representing the position of the lesion over this 3D body mark.
With the prior art discussed in Literature 1, information about the lesion indicated by the prone position MRI image could not be displayed on the body mark. Even if a conversion rule could be found that would do coordinate conversion of the position of a lesion on a body mark on the basis of the external shape of a breast obtained from an MRI image, the displayed position of the lesion will deviate from the actual position. The reason this deviation occurs is that the difference in the physical distortion state of the breast during imaging between ultrasound and MRI is not taken into account. Accordingly, probe manipulation cannot be properly facilitated.
Also, even if a supine position 3D body mark is produced on the basis of the methods in the above-mentioned Literature 3 and 2, the shape of the body mark will not be simplified or normalized, so making a contrast to a standard position expression A region, B region, etc.) is not intuitive. Accordingly, this is not suited to use in a medical document such as an electronic chart or an image diagnostic report.